/*
 * (c) Copyright 2009 Hewlett-Packard Development Company, LP
 * All rights reserved.
 * [See end of file]
 */

package com.hp.hpl.jena.clusteredtdb.base;

import java.util.Iterator;

public class ThreadedBufferedIterator<T> extends BufferedIterator<T> {

	Object lock;
	boolean bufready;
	BufUpdater<T> bufUpdater;
	//TODO implement remove, etc
	
	public ThreadedBufferedIterator(int bufSize, IteratorProcessor<T> worker) {
		super(bufSize,worker);
		this.lock = new Object();
		bufready = false;
		bufUpdater = new BufUpdater<T>(this,worker,bufSize, lock);
		new Thread(bufUpdater).start();
	}
	
	//TODO: double-buffer and multi-thread this process
	@Override
    public boolean hasNext() {
		if (buf1 == null || buf1.hasNext() == false) {
			synchronized(lock) {
				if (!bufready) {
					try {
						lock.wait();
					} catch (InterruptedException e) {
						// TODO Do something nice here
					}
				}
				buf1 = this.bufUpdater.getBuf();
				bufready = false;
				lock.notify();
			}
			
			
		}
		return buf1.hasNext();
	}
	
	static class BufUpdater<T> implements Runnable {

		ThreadedBufferedIterator<T> parent;
        IteratorProcessor<T> worker;
		Iterator<T> buf;
		int bufsize;
        Object lock;
		
		public BufUpdater(ThreadedBufferedIterator<T> parent, IteratorProcessor<T> worker, int bufsize, Object lock) {
			this.parent = parent;
			this.worker = worker;
			this.bufsize = bufsize;
			this.lock  = lock;
		}
		
		public void run() {
			synchronized(lock) {
				while(true) {
					if(parent.bufready == true) {
						try {
							lock.wait();
						} catch (InterruptedException e) {
							// TODO Do something nice here
						}
					}
					buf = worker.getChunk(bufsize);
					boolean exit = (buf == null || buf.hasNext() == false);
					parent.bufready = true;
					lock.notify();
					if (exit) {
						break;
					}
				}
			}
			
		}	
		
		public Iterator<T> getBuf() {
			return this.buf;
		}
		
	}
	
}

/*
 * (c) Copyright 2009 Hewlett-Packard Development Company, LP
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
